Try all of these recipes on the whole group before the trip for no surprises when you are a day away from the vehicle.
Trail Pizza: Pita or small Boboli topped or filled with a little pizza sauce from a jar or a can of spiced tomato sauce, light dusting of onion powder, very thin sliced cheese, and a small amount of pepperoni, canned olives, canned mushrooms. The sauce is only safe for the one meal when you open it.
Instant mashed potatoes rehydrate fine without heat but are high salt content. Before the trip, I add dried milk for creaminess, onion powder, garlic powder, and low salt chicken broth to boost the flavor. Sarah and Laurie probably have extensive potato recipes, and I second Dicentra's taco tater recipe using dehydrated beans to flavor potatoes. At home, powder the bean flakes in a ziplock using a rolling pin because the powder will rehydrate in unheated water more easily than the flakes.
Quick oats soak in unheated water, then add powdered milk and raisins, with pudding mix to thicken it. Add cinnamon, allspice, and nutmeg to the dry oats at home. Add nuts and banana chips to make it chewier. Time the required soaking at home before the trip. I add instant hot chocolate mix to flavor mine.
Bring Koolaid for those who are avid pop drinkers.
Instead of a large quantity of one trail mix, bring many different mixes. Kids may like to personalize one mix by adding their favorite ingredients.
Desserts in the Desert: Tropical trail mix is mostly dried fruit. Some will like the sweetness. Banana pudding mix made with dry milk with added nuts, banana chips, and coconut flakes make it chewy so it lasts longer when eating it. Bring chocolate pudding mix for those suffering from chocolate withdrawal.